Some prior art agricultural and/or industrial irrigation systems comprise a conduit for supplying an irrigation liquid, generally water, which is connected to a plurality of sprinkler devices for uniformly distributing a liquid jet to a soil portion to be irrigated.
Particularly, these sprinkler devices may be either stationary, to always irrigate the same soil portion, or movable relative to the supply conduit for substantially constant-speed sweeping of a given cultivated surface.
In view of improving jet orientation, articulated joints have been developed, which are interposed between the liquid supply conduit and the sprinkler device and are adapted to adjust the inclination angle of the jet relative to the ground.
Articulated joints can adapt jet distribution to current weather conditions, e.g. by compensating for any liquid deflection caused by the wind.
EP0544688, by the applicant hereof, discloses an articulated joint for irrigation system jets which comprises a first curved tubular body, adapted to be connected to the jet, and to slidingly fit into a second curved tubular body that is adapted to be secured to the liquid supply line. The relative inclination angle of the two bodies can be adjusted by the user by screwing/unscrewing a threaded shaft with respect to a pair of pins that are joined to the first and second tubular bodies respectively. Thus, by causing the shaft to be entirely screwed or unscrewed with respect to the pins such inclination angle may be continuously adjusted in a predetermined range from minimum to maximum values.
The main drawback of this solution is that the inclination of the tubular bodies of this joint may change with time, thereby causing an unexpected change in liquid distribution over the soil.
This is because the position of the threaded shaft may change due to pulling forces acting on the joint, as a result of vibrations or water hammers caused by the jet.
In an attempt to obviate this drawback, articulated joints have been developed which afford discrete adjustment of the inclination angle in a predetermined range from minimum to maximum values.
EP0185901, also of the applicant hereof, discloses an articulated joint having a pair of tubular elements sliding one into the other with respective mutually facing upper bored appendices. An arched slot is formed in one of the appendices, whereas the other appendix has a plurality of holes for receiving a screw. By introducing the screw into a given hole, the limits of the range of inclination angle adjustment for the jets relative to the ground may be discretely changed.
A first drawback of this arrangement is that this joint only affords discrete selection of the limits of the inclination angle adjustment range.
The intermediate inclination angle values shall still be adjusted manually by appropriate displacement of the slot and are thus still exposed to the risk of changing with time due to variations, water hammers and other impulsive forces that may be exerted on the sprinkler.
A further drawback of this arrangement is that the joint affords adjustment of the inclination angle in a limited range, generally not exceeding 25°.
Furthermore, the maximum inclination angle adjustment for each adjustment range is very small, not exceeding about 6°.
Another drawback of this arrangement is that the appendix of each tubular portion is placed on the upper portion of the joint, which will increase the overall dimensions and cause a higher risk of unexpected failures thereof, as a result of accidental impacts of the appendix against other parts of the irrigation system.
Furthermore, these joints have poor stability and durability, as the portions of the body that are designed to slide one unto the other are exposed to wear, thereby affecting fluid tightness and causing liquid leakage.
These impacts are very frequent during installation of the joint in the system.